docs: def get_labels(input_dir):
    """Get a list of labels from preprocessed output dir."""
    data_dir = _get_latest_data_dir(input_dir)
    labels_file = os.path.join(data_dir, 'labels')
    with file_io.FileIO(labels_file, 'r') as f:
      labels = f.read().rstrip().split('\n')
    return labels